上层大气中铁质流星尾迹的紫外光谱模拟

基于 Sparrow理论 ,计算了海拔 90— 95 km高空的不同初始地心坐标速度的典型铁质流星的有效温度 ,获得初速 72 km/ s的该类流星尾迹主要成分的粒子数密度 ,以 Cloudy程序模拟了该流星尾迹的 2 0 0—4 0 0 nm波段紫外辐射 ,给出了若干预期的强谱线的相对强度     

狮子座流星雨纵横谈

 根据天文学家预测,33年一遇的狮子座强流星雨将出现在1998年11月18日凌晨2～4时;预计在流星雨最高峰时,每小时划过夜空的流星数可能会超过10万颗,射向四面八方的流星好似节日的礼花烟火,放射出璀璨的光芒;我国东北部的居民处于最佳观测位置,其他地区的人们均可看到规模不同的流星雨.     

高速模型尾迹流场及其电磁散射特性相似性实验研究

高速目标再入大气层或在临近空间飞行时,空气电离形成的等离子体鞘套和尾迹对目标的雷达散射特性会产生影响.为了研究不同模型尾迹流场及其电磁散射特性规律和相似性,以氧化铝球模型为研究对象,在弹道靶设备上开展了双尺度参数相同的条件下高速球模型尾迹流场及其电磁散射相似性实验研究.由二级轻气炮发射模型,模型直径分别为8.0、10.0、12.0、15.0 mm,速度约6 km/s,靶室压力分别为6.3,5.0,4.2,3.3 k Pa,采用阴影照相系统测量模型激波脱体距离、电子密度测量系统测量模型尾迹的电子密度分布、X波段单站雷达系统测量在视角为40?的模型及流场的雷达散射截面(RCS)分布.实验结果表明:在速度不变、双尺度参数相同的条件下,随着模型尺寸的增加,激波脱体距离逐渐增加,激波脱体距离与模型直径之比近似相同;不同模型尾迹电子密度测量曲线的趋势和数量级一致,表明不同模型的尾迹流场适用于双缩尺律;不同尺寸模型尾迹的总体RCS与分布RCS均不相同,表明不同模型尾迹的电磁散射不适用于二元缩尺律;高速球模型全目标电磁散射能量分布在模型及其绕流区域、等离子体尾迹区域;高速球模型全目标电磁散射能量在模型及绕流场区域出现1个强散射中心,在模型湍流尾迹区域出现多个散射中心;高速球模型尾迹的RCS测量信号呈现随机性分布特性,幅度脉动和频率脉动均没有周期性;随着模型尺寸的增加,模型尾迹的总体RCS增加,尾迹脉动频率的变化范围减小.     

亚音速、跨音速轴流压气机叶栅尾迹特性的研究——平均流动模型

在本文中,作者提供出叶栅在不同工作条件下比较完整的尾迹平均图形,并首次提出了用尾迹特性参数所表示的尾迹中气流最小速度与自由气流速度比的控制方程,采用文中所提供出来的方程和方法,经过实验和实践证明,可以认为是有效的。     

短波近红外光谱的整粒小麦蛋白质PLS方法的定量分析

利用漫反射法获得的整粒小麦短波近红外光谱(833～1111nm),采用化学计量学中的偏最小二乘法(PLS)方法,选取不同的波长范围对光谱进行信息提取和分析,给出了不同因子数时PLS方法进行蛋白质分析的结果及其因子数与预测标准偏差平方和(PRESS)关系曲线,确定了最佳回归因子数。并通过选取最佳回归因子和不同波段,对整粒小麦的蛋白质成分进行了定量分析,比较了不同波长范围对分析的影响,并从中获得了较好的预测结果,实验表明,合理选择光谱范围可减少非主要信息的干扰,并以此来提高成分分析精度的方法是切实可行的,在实际应用中有一定的参考价值。     

低雷诺数下周期性尾迹／层流分离泡相互作用的大涡模拟

本文采用大涡模拟(LES)方法,对低雷诺数条件下周期性尾迹/层流分离泡的相互作用进行了数值模拟.计算域入口尾迹采用独立计算的平面尾迹流给出.对周期性尾迹作用下的层流分离泡进行了统计特性及瞬态流场分析,并与相同条件下的无尾迹流动进行比较.计算结果表明:在尾迹作用下,时均层流分离泡长度明显缩短,分离泡变小;相位平均的分离点/再附点随时间不断变化;从瞬态结果容易看出,尾迹诱导的流向涡结构是导致分离泡提前转捩的主要原因.     

汽车车身油漆红外光谱特征

采集了287份汽车车身油漆样本,使用傅里叶变换显微红外光谱仪获取了940份油漆层光谱,对不同车型、颜色的汽车油漆的清漆层、面漆层、中涂层的光谱特征进行分析,并对其光谱相似度进行比较。结果表明,同车型不同颜色的清漆层光谱相似度达到99.5%,部分相近车型的清漆层光谱高度相似;面漆层光谱因车型、颜色不同而差异较大,相似度在70%以下;中涂层的普通腻子光谱间的相似度在83.33%～96.91%,水基腻子光谱间的相似度在70.12%～96.44%;油漆中的金属成分会影响面漆层光谱的吸收特征;汽车油漆光谱随使用时间变化而发生变化。     

基于逐步回归法的近红外光谱信息提取及模型的研究

基于多元线性回归的逐步分析算法 ,依据小麦粉的近红外吸收特性机理 ,对小麦粉的近红外光谱(10 0 0～ 2 5 0 0nm)划分三波段 (Ⅰ :10 0 0～ 14 0 0nm ;Ⅱ :14 0 0～ 186 0nm ;Ⅲ :186 0～ 2 5 0 0nm) ,并进行了各波段的光谱信息提取 ,确定了回归特征波长 ,对不同波段建立的回归模型进行了比较 ,给出了各段回归的最佳数学模型。通过对小麦粉近红外谱的信息提取及蛋白质成分的定量分析 ,比较和讨论了不同波段所建模型对小麦粉蛋白质含量的近红外分析结果 ,在应用中有一定的参考价值。     

水平轴风力机叶尖涡流动的PIV测试

在风洞开口实验段,针对不同尖速比应用PIV技术对风轮附近1/3圆周内的瞬时速度场进行测试。随着尖速比的增加,叶尖涡运动的径向位移增大,涡流诱导效应区域半径扩大,使整体尾迹半径增大;同时,尖速比增加使尾迹轴向速度亏损增大,叶尖涡运动的轴向位移减小。叶尖涡诱导效应与风轮旋转的相互作用使风轮附近形成强速度梯度区域,诱导效应延伸到风轮上游,激励叶片产生不同的振动形态,使叶片上脱落的叶尖涡结构在尾迹中出现波动,越向下游运动波动越强烈。通过叶尖涡核位置平均发现,在10°～120°方位角尾迹区域内,涡核运动轨迹与方位面交点的连线近似为直线,且该线的斜率随着尖速比的增加而增大。     

再入体缩比模型湍流等离子体电磁散射特性测量

介绍了在弹道靶上利用二级轻气炮发射再入体缩比模型开展湍流等离子体电磁散射特性模拟试验方法、湍流等离子体的雷达散射截面积(RCS)测量方法。给出了模型尾迹湍流等离子体的电磁散射特性测量典型试验结果,对获得的试验结果进行了分析,并与一阶畸变波Born方法计算结果进行了比较。结果表明:合理选择缩比模型发射速度和飞行环境压力,在弹道靶上能够模拟产生湍流等离子体;利用激光阴影成像技术获得的锥模型尾迹流场图像证实了尾迹转捩的出现及其湍流形成;在给定的试验条件下,锥模型及其绕流RCS测量值比其尾迹RCS测量值高3个数量级,比背景散射电平高0.5~2.5个数量级,且信号没有周期性,幅度脉动范围为1~15dB,频率脉动范围0.4~40kHz;锥模型湍流尾迹RCS的脉动可能是尾迹电子密度的脉动引起的;单站X波段雷达系统测量的锥模型尾迹亚密湍流等离子体的散射信号测量值与计算结果变化规律一致;弹道靶RCS测量技术可用于再入体缩比模型湍流等离子体电磁散射特性研究,为开展相关研究提供了一种有效的地面模拟实验研究途径。     

Study of the Influence of the Mutual Orientation of Antennas on the Characteristics of a Meteor Radio Channel

We describe equipment and a method for performing an experiment on a short meteor radio line of length 85 km. The feature of the experiment is monitoring of meteor-matter deposition to the atmosphere using a radar located at one point of the radio line with the simultaneous determination of the main radio-line characteristics.     

Computer model of a meteor radio channel

A computer model of a meteor radio channel is presented. The model is based on the Monte-Carlo method. The possibility of effective choice of the model parameters is proved. The simulation results agree well with the experimental data obtained in meteor radio lines with lengths of 240, 700, and 1100 km.State University, Kazan. Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Radiofizika, Vol. 38, No. 11, pp. 1177–1186, November, 1995.     

Baseline effect on the forward-scatter radar reflections from meteor trains

Summary The influence of the baseline orientation on the rate of recorded meteor echoes has been shown from the observations carried out during the Lyrid meteor shower periods in 1992 and 1993 with receivers rectangularly displaced from the transmitting station in Bologna with a baseline length of about 700 km. It is shown that the maximum echo rate precedes or occurs later than the shower radiant culminates (at heights of 80°), favouring the 45° radiant elevation and similar angle between the radiant and the beam axis. The consequences of the measured effect on the meteor flux within the shower and sporadic radiant distribution is discussed.     

Radiowave propagation on short meteor radio links

We present experimental results obtained on meteor radio links with lengths of 100 and 250 km. The advantage of the “lateral propagation” is demonstrated. Using the “KAMET” computer model, we simulated the propagation of radiowaves along radio links, of up to 600 km. An effective version is proposed for working on radio links of up to 300 km, which is called “tracking the meteor activity maximum.” State University, Kazan’, Russia. Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Radiofizika, Vol. 40, No. 6, pp. 693–703, June, 1997.     

Underwater surf noise near sea coasts of different types

Data on underwater surf-generated noise measured near stony, rocky, and sandy coasts of the Black Sea and the Pacific Ocean are presented for a frequency band of 0.03–16 kHz and distances of 0.01–30 km from the coastline. The frequency-power spectra and the excess coefficients in the distributions of the instantaneous values of sound pressure in surf-generated noise are considered for coasts of different types. At surface wave heights of 0.5–0.8 m, the surf-generated acoustic noise near pebble-type coasts is higher than the noise of the open sea at a distance of 10 km from the coast, while the excess coefficients are positive at distances of up to 2.7 km from the coast.     

Radio echoes from long-enduring meteor trails as a tracer of small-scale internal gravity waves

Summary Radar data from long-enduring meteor trails observed during two different campaigns carried out at the CNR station in Budrio (45° N, 11° E) near Bologna in Autumn of 1980 and 1985 reveal that the wave field near the mesopause is composed of a superposition of wave motions to be connected possibly to propagating internal gravity waves. The measured vertical wavelengths ranged from 2 to 13 km with dominant wave activity at values between (2÷3) km and (6÷7) km. The observed small-scale wave activity suggests processes and effects of wave field saturation and of convective or dynamical instability.     

On the activity and orbit of the Geminids meteorid stream

Summary The activity of the Geminids meteor shower is studied on the basis of radio observations carried out by the Budrio meteor radar in 1986. The 1986 Geminids have displayed as a distinct meteor shower with an asymmetric curve of activity, the duration between the points of one-quarter strength being 6 days and the maximum at the solar longitude of about 260°.75 (1950.0). The mean orbit and radiant ephemeris of the Geminids are derived on the basis of 191 precise photographic orbits available from the IAU Meteor Data Centre in Lund. Over a time span of 50 years, the semi-major axis, eccentricity and perihelion distance of the stream exhibit variations following the trend of the stream evolution suggested by Williams and Wu.     

Vertical motions in the lower ionosphere and a sporadicE-layer

We propose a calculation technique for the main characteristics of a sporadic E-layer, including the effective recombination coefficient, the relative content of meteor and atmospheric ions in the layer, and the time of its evolution. This technique is based on measurements of vertical plasma velocities by the method of resonance scattering of radio waves by artificial periodic inhomogeneities of the electron density. The contribution of internal gravity waves and turbulent motions to the formation of sporadic layers is estimated. The characteristic values of the turbulent velocity measured by this method at the heights of the turbopause are presented. The possible mechanisms of mid-latitude sporadic E-layer formation at heights of 90 to 120 km are considered. Experimental studies confirmed the main statements of the wind shear theory concerning the determining role of the redistribution of ionization under the action of atmospheric winds with vertical gradient of velocity in the formation of E_s. Deceased. Radiophysical Research Institute, Nizhny Novgorod, Russia. Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Radiofizika, Vol. 42, No. 1, pp. 26–35, January, 1999.     

基于MATLAB的尾流图像数字化处理

介绍了尾流图像数字化处理工作原理及方法.用MATLAB软件对船舶时速分别为30 km/h和40 km/h的两幅尾流图像进行了灰度变换、滤波、Canny边缘化、二值变换、直方图变换等,并对实验结果进行了初步分析,得到了船舶航速影响尾流边缘夹角、边缘弯曲度及直方图峰值变化.研究结果为尾流图像进入信息化系统提供了基础.     

A new method of discovering new meteor showers from the IMO single-station video meteor database

It has been found that unknown meteor showers could be efficiently discovered from the single station video meteor database of the International Meteor Organization (IMO) by assuming the geocentric velocity and adjusting it within the dynamically permitted range. The mean geocentric velocities of new meteor showers can be obtained, as well as the coordinates of the radiants. The activity period and maximum time can also be obtained if there are sufficient shower meteors. All single station video meteor observations between February 13 and 17 (from 2000 to 2005) in IMO’s database are processed with this method. As a result, two new meteor showers, one near RA=245.10°, Dec=41.82° in Hercules and the other near RA=233.03°, Dec=17.04° in Serpenids, are discovered. Some dynamical characteristics of the new meteor showers are also determined. Considering the random nature on the selection of period in this work, it is expected that there are some more potential new meteor showers in IMO’s video database. Supported by the National Natural Science Foundation of China (Grant No. 10373004)